A new perspective on the CMSSM: Yukawa Unification, DM and the SUSY scale

Abstract

What does third family ($t$-$b$-$\tau$) Yukawa unification, a typical prediction from embedding the Standard Model (SM) fermions in 16-plets of a $\mathrm{SO}(10)$ GUT, imply for the scale of the supersymmetric (SUSY) partners? Which neutralino dark matter (DM) candidate can be realized, and how large is the DM relic density? In this work, we address these questions in a simplified SUSY-breaking framework: the Constrained Minimal Supersymmetric Standard Model (CMSSM). To this end, we recast the parameter space of the CMSSM in a way that for all parameter points the SM-like Higgs mass is correctly reproduced. Considering fixed $\tan\beta$ and $\mathrm{sgn}(\mu)$, for every point in the $(x:=\frac{M_{1/2}}{m_0},y:=\frac{A_0}{m_0})$ parameter plane ranges for all observables are predicted. This provides a new perspective on where in parameter space different types of DM are realized, and which value of the SUSY scale is required in order to explain the observed mass of the SM Higgs boson. In our analysis we consider and compare two strategies: grid scans over the $(x,y,\tan\beta)$ parameter region and MCMC sampling. We find both techniques yield similar results. For $t$-$b$-$\tau$ unification within $5\,\%$ or $10\,\%$, we find $\mu<0$, the SUSY spectrum showing a characteristic pattern, and the SUSY scale around $\mathcal{O}(10)\,\mathrm{TeV}$. The extra MSSM Higgses are the lowest lying new states at $\sim 2\div 3\,\mathrm{TeV}$ (with discovery potential at the HL-LHC), the $\mathcal{O}(10)\,\mathrm{TeV}$ stops and gluino are in reach of a possible FCC-hh, while bino DM has a mass above $2.5\,\mathrm{TeV}$, is overabundant, and effectively unobservable in planned direct and indirect detection experiments. The DM relic density requires a dilution factor of $10<\mathcal{D}<1000$, implying non-standard cosmology that could leave its imprints in the stochastic gravitational wave background.